1. Field of the Invention
Aspects of the present invention relate to an electrolyte membrane using a polybenzoxazine compound and a method of manufacturing the same, and more particularly, to an electrolyte membrane of a fuel cell for high temperature and low humidity conditions, and a method of manufacturing the same.
2. Description of the Related Art
In conventional ionic conductors, ions are moved by applying a voltage. Ionic conductors are widely used in electrochemical devices, such as fuel cells, electrochemical sensors, and the like.
For example, in terms of energy generating efficiency, system efficiency, and component durability, fuel cells require a proton conductor that exhibits long-term stable proton conductivity at an operating temperature of 100 to 300° C. under non-humidified conditions or low-humidified conditions such as a relative humidity of less than 50%.
The above requirements have been considered in the development of conventional solid polymer-type fuel cells. However, solid polymer-type fuel cells that include a perfluorocarbonsulfonic acid membrane as an electrolyte membrane generates insufficient energy at an operating temperature of 100 to 300° C. in a relative humidity of 50% or less.
Conventional fuel cells include fuel cells using an electrolyte membrane containing a proton conducting agent, fuel cells using a silica diffusion membrane, fuel cells using an inorganic-organic composite membrane, fuel cells using a phosphoric acid-doped graft membrane, and fuel cells using an ionic liquid composite membrane.
In addition, a solid polymer electrolyte membrane formed of polybenzimidazole (PBI) in which a strong acid, such as a phosphoric acid or the like, is doped is disclosed (in U.S. Pat. No. 5,525,436). In such an electrolyte membrane, ionic conductivity is increased by phosphoric acid doping, but the phosphoric acid doping causes the mechanical properties of the electrolyte membrane to deteriorate. In particular, PBI doped with a strong acid such as a phosphoric acid lacks mechanical strength and chemical stability at high temperatures, and the liquid supplementing capability of the phosphoric acid decreases.